This invention relates to elongated buoyant marine devices, the displacement of which decreases during operation as a result of weight loss, such as pyrotechnic marine markers. The invention relates more particulary to improved devices of this type which are more capable of retaining proper operative orientation during their functioning.
Marine markers are frequently used as signalling devices for example they may be displayed in conjunction with sonobuoys by long range marine patrolaircraft during anti-submarine operations. They may also be used for search and rescue operations, for example to mark a wreckage site, or to mark a position at sea (icefloes, oil slicks). These markers are designed to produce smoke and an intense flame, generally by the burning of a pyrotechnic candle or flare. The flare is usually enclosed in an elongated jacket, and for example may consist predominately of red phosphorus which produces dense white smoke and a yellow flame for a period of thirteen to nineteen minutes from time of ignition by a salt water-activated battery and squib combination. Although the marker initially floats vertically in the water, the increase in buoyancy after several minutes of burning causes it to cant until, as the burning continues, the marker usually finally ceases burning in an almost horizontal position on the surface of the water. In other words, because the weight of the marker decreases as the flare burns, its displacement is greater at the beginning of its operation than at the end. As burning continues the marker gradually rises in the water and slowly begins to tip as the burning progresses until, at a time for example halfway through the burn time, it reaches an almost horizontal position which it retains until the end of the burn.
In this final position the combustion gas outlet at the top of the marker is nearer the water than when the marker is in a vertical position. The marker may thus be more easily submerged by waves; water penetrating the marker through the gas outlet can hamper the operation of the marker and cause the flare to burn intermittently or incompletely.
Under ideal burn conditions, for example in calm water where the problem of water penetrating the marker does not arise, the marker will burn continuously for the specific period for which it was designed. In practice however ideal conditions do not prevail and because the markers may burn intermittently or incompletely, it follows that, to obtain effective production of flame and smoke for a given time, a greater number of markers must be used than would be required under ideal burn conditions.
Some marine devices have a flotation collar fitted around their upper part to ensure that the device remains in an upright position while it operates. Flotation collars are made of a rubber-like material which inflates when the device enters the water, or of a buoyant material such as foam rubber or the like. Such flotation collars significantly increase the size and cost of such devices.
Accordingly it is an object of the present invention to provide an effective, more economical construction for such marine marker and other elongated buoyant marine devices, the displacement of which decreases during operation as a result of weight loss, which will be effective in maintaining the device in a vertical, or close-to-vertical, operative position.